Technical Field
The present disclosure relates to a transmitter. More particularly, the present disclosure relates to a transmitter with compensating of pulling effect and an eliminating method thereof.
Description of Related Art
In various wireless communication systems, a transmitter can modulate the frequency, by using an oscillating signal generated from an oscillator, to generate a radio frequency signal that is suited for the wireless communication. However, as the size of transmitters become smaller and smaller, such a radio frequency signal could be inadvertently coupled back to the oscillator. As a result, a phase error may be introduced into the oscillating signal, and thus the overall performance of the transmitter may be reduced. The aforementioned phenomenon is commonly known as the “pulling effect.”
In some approaches, the calibration mechanism for eliminating the pulling effect is arranged subsequent to a mixer. As a result, the required bandwidth for such calibration mechanism may be too high. The cost and complexity of the transmitter are thus increased. In some other approaches, the calibration circuit for eliminating the pulling effect is arranged in a phase locked loop. As a result, unwanted phase noise may be introduced and this may reduce the performance of the transmitter.